An agricultural seeding machine such as a row crop planter or grain drill places seeds at a desired depth within a plurality of parallel seed trenches formed in soil. In the case of a row crop planter, a plurality of row crop units are typically ground driven using wheels, shafts, sprockets, transfer cases, chains and the like. Each row crop unit has a frame which is movably coupled with a tool bar. The frame may carry a main seed hopper, herbicide hopper and insecticide hopper. If a herbicide and insecticide are used, the metering mechanisms associated with dispensing the granular product into the seed trench are typically relatively simple. On the other hand, the mechanisms necessary to properly meter the seeds, and dispense the seeds at predetermined relative locations within the seed trench are relatively complicated.
The mechanisms associated with metering and placing the seeds generally can be divided into a seed metering system and a seed placement system which are in series communication with each other. The seed metering system receives the seeds in a bulk manner from the seed hopper carried by the frame. Different types of seed metering systems may be used, such as seed plates, finger plates and seed disks. In the case of a seed disk metering system a seed disk is formed with a plurality of seed cells spaced about the periphery of the disk. Seeds are moved into the seed cells with one or more seeds in each seed cell depending upon the size and configuration of the seed cell. A vacuum or positive pressure air differential may be used in conjunction with the seed disk to assist in movement of the seeds into the seed cell. The seeds are singulated and discharged at a predetermined rate to the seed placement system.
The seed placement system may be categorized as a gravity drop system or a power drop system. In the case of the gravity drop system, a seed tube has an inlet end which is positioned below the seed metering system. The singulated seeds from the seed metering system merely drop into the seed tube and fall via gravitational force from a discharge end thereof into the seed trench. The seed tube may have a rearward curvature which reduces bouncing of the seed as it strikes the bottom of the seed trench.
Conventional techniques for providing rotary power to turn individual seed meters on each row unit of a seeding machine include: a central ground drive transmitted through complex shafting systems; hydraulic motors to turn a complex shafting system which in turn fans out to drive each seed meter; or an electric motor on each row unit to provide the rotational drive to control and drive the corresponding seed meter. Each of these approaches has some major cost, space, reliability, or control disadvantages. Mechanical rotary power transmission has many shafts, chains, bearings, and couplers to cross over frame flex and fold pivots. Individual control of seeding rates is not easily accomplished even with hydraulic drives. Electric motor drives are costly but do offer individual rate control including single row drive disconnects. A disadvantage of electric drives besides cost and generating enough electrical power to handle multiple row machines, is power cable handling and routing through the large machine space frames, across flex and fold pivots, etc.
What is needed in the art is a seeding machine with a seed metering system that allows individual control of the seed meters, while avoiding the disadvantages described above.